A systematic review of 42 randomized controlled trials evaluated the effects of music in multiple peri-operative settings and found that the intervention had positive effects in reducing patient pain and anxiety in approximately half of the reviewed studies (Nilsson, 2008). Many included trials were noted to be of "insufficient quality" and a meta-analysis could not be performed due to variation in the types of music used, the duration of listening time, and procedures investigated. Furthermore, some studies used non-validated questionnaires and had other methodological limitations. Nonetheless, the author concluded that peri-operative musical interventions are easy to implement and effective in reducing patient pain, anxiety, and stress (Nilsson, 2008).